Why would my gasket blow without no warning of it over heating, only 67000miles

Yes I had it checked out, I did get an oil change 2 miles before it blew. The same place that changed the oil, worked on it for a few hour to figure out the problem. I know that the oil filter was loose , so I thought they were at fault. They spent a few hours on it and said # 1 & 2 gaskets were blown. How could this happen? They said no water was in the engine. They started it up and said it didn't start right away, but when I got in and started it there was no problem, and all the lights were off( cvs, ect.) I'm not sure where to go with this.